1. Field of the Invention
The present invention relates to a cell storage bag system and a method of storing cells, and in particular relates to a cell storage bag system for storing cells such as red blood cells, white blood cells and blood platelets that have been separated from an extracted portion of blood, and also relates to a cell storage system for use in the cultivation of cells in a liquid medium.
2. Description of the Prior Art
In recent years, in order to prevent the spread of infectious diseases (for example, hepatitis, AIDS and the like) and the occurrence of immunological side effects as a result of blood transfusions between two different people having the same blood type, the practice of receiving a transfusion of one's own blood has gained attention. Among the methods for the transfusion of one's own blood, there is known a storage type transfusion. In the storage type transfusion, a blood reserve is established by removing blood from a patient (blood donor) prior to undergoing surgery and storing such removed blood in a blood bag which is itself then stored in a storage container for preserving the stored blood. Then, at the time the patient is to undergo surgery, the blood bag is removed from the storage container and the patient's blood stored therein is used to give the patient any needed blood transfusions during the course of the surgery.
At the time when such blood transfusions are being carried out, it is necessary to ensure that there is an adequate volume of blood available for transfusion, and this is done by carrying out one of several methods. In one method, this is accomplished by freezing the liquid blood stored in the blood bag. In another method the blood is maintained in liquid form in the blood bag, for example, employing the leap-frog method or the switch-bag method. In the switch-bag method, before the day of the surgery the blood that was previously stored is returned to the patient and then twice volume of the blood is once again extracted from the patient and stored. By employing these type of methods, it is possible to ensure a relatively large amount of fresh blood in a short period of time.
However, in order to employ the first method mentioned above, it is necessary to have the proper equipment for freezing the samples, and in addition to the maintenance that is required for such equipment, an inappropriate amount of time, labor and cost is required for freezing and thawing blood stored in the blood bags. As for the second method mentioned above using the switch-bag method, the frequent extraction and transfusion of blood results in a high physical burden on the patient. Further, if such methods are carried out by using the conventional blood bags, this method is unavoidably complicated due to the structure of the bags.
Moreover, with regards to the second method mentioned above, the effective storage period of the blood is rather short, and therefore there is a disadvantage in that it is sometimes not possible to store a sufficient amount of blood over such time period. Consequently, in order to overcome this disadvantage, in recent years much attention has been give to methods that make it possible to prolong storage times by exchanging preserving fluids.
This method involves the use of a multiple bag system in which a plurality of bags are joined by tubes. In this system, one bag is used for storing blood, and two other bags are divided into one bag that holds a fluid for preserving red blood cells and a second bag for holding waste fluids. During the storage of blood, supply of a nutrient source such as glucose and the like which is performed by supplying preserving fluid and removal of waste products such as lactic acid and the like contained in the fluid are performed in order within a closed system. This method, in comparison with the first and second methods mentioned above, makes it possible to greatly extend the length of time that the blood can be stored, and because this results in a lengthening of the interval between blood extractions, the burden on the patient is diminished. Therefore, this method is considered to have good future prospects.
However, in the method employing the multiple bags described above, because each bag is joined to each other, the preserving fluid and waste fluid must be stored together with the stored blood, which gives rise to the disadvantage that it becomes necessary for there to be a rather large storage space. Also, in order to separate out the preserving fluid in the blood bag in which waste products have been accumulated as waste fluid, the blood storage bag must centrifuged, and in this case it becomes necessary to carry out such centrifugal separation operation on all the bags of the multiple bag system. However, at the present time, the size of the centrifuging cup of centrifuging separators which are available does not allow the placement of five or more storage bags. Accordingly, multiple storage bag system must be limited to at most four bags, which places an upper limit on the amount of preserving fluids and waste fluids that can be contained by a multiple bag system.
Moreover, with the multiple bag system, when the blood storage bag is to be carried somewhere, all the other multiple number of bags that are joined therewith must also be carried together at the same time. Consequently, during transport of the multiple bag system, there is an increased likelihood of the bags being dropped or the bag system being damaged due to the connecting tubes being pulled. Furthermore, due to the unnecessary bags which are always attached thereto, when a fluid to be stored is being poured into the storage bag or when other storage operations are to be carried out, it is difficult to carry out such operations. Further, the time needed to complete such operations are increased, and this cumbersome arrangement also makes it easy for misoperations to occur.
Meanwhile, as general methods of cultivating cells, there is a method in which such cultivation is taken place by dispersing cells within a liquid medium stored inside a storage bag. When employing this type of cultivation method, in order to maintain the activity of the cells, it is necessary to change the liquid medium at regular intervals.
Up to now, liquid mediums have been changed by carrying out a method like the one that follows. Namely, the cell cultivating bag is placed on a clean bench or the like and a section of the tube connected therewith that is to be cut is sterilized with alcohol, and then that section of the tube is cut using a cutting tool such as a knife or scissors which have been heat sterilized. Then, the cell cultivating bag is lightly pressed to discharge the used up liquid medium out through the tube to be collected into a beaker or the like, and then the discharged liquid medium is collected. Next, fresh liquid medium contained in a cultivating medium preserving bag is transferred to the cell cultivating bag by inserting a needle, which is provided on the end of a liquid medium supply tube connected to the cultivating medium preserving bag, through a guiding portion of the cell cultivating bag and then passing the fresh liquid medium from the cultivating medium preserving bag through the liquid medium supply tube into the cell cultivating bag.
However, in the change method mentioned-above, because it is impossible to carry out exchange of the liquid mediums within a closed system, it is difficult to maintain sterile conditions. Consequently, at such times when the tube and the cutting tool are undergoing sterilization and when the liquid medium is being discharged, it is necessary to exercise extreme care in order to prevent bacterial contamination from occurring, and this labor intensive process results in a reduction in work efficiency.